$1)$ Shake Shack is $70\%$ funded with debt at an after$-$tax cost of $9\%,$ while the cost of equity is $12\%.$

What is Shake Shack$$s weighted average cost of capital $($WACC$)?$

a$)9\mathrm{.}0\%$

b$)12\mathrm{.}0\%$

c$)10\mathrm{.}5\%$

d$)9\mathrm{.}9\%$

e$)0\mathrm{.}0\%$